Matching fluid

To test the influence of a change in the ambient refractive index on the laser spectrum, the CBNL was immersed in a specially designed beaker containing index-matching fluids with different index of refraction. For each fluid, the emitted spectrum is measured (fpump 2.5 mW). 

When tested according to USP general test <271>, the resulting solution can have no more color than Matching Fluid Q. 

Index Matching Fluid—A fluid with an index of refraction close to that of glass that reduces reflections caused by refractive-mdex differences. 

The original powder SHG method is due to S. Kurtz and T. T. Perry (13). There have been variations and improvements reported since that work(14). In the basic method, a fine powder is loaded into a holder such as a cuvette. The pathlength of the cell should be much larger than the particle size to ensure sampling of many particles. The particles may be immersed in an index matching fluid. Without index matching fluid,... 

We have recently conducted a set of intracavity second harmonic generation experiments using the organic nonlinear material DAN (4-(N,N-dimethylamino)-3-acetamidonitrobenzcne) and an optically pumped cw Nd YAG laser (2). Figure 3 shows the experimental setup. Quasi-cw operation was achieved with crystal samples immersed in index matching fluid in an antireflection coated cuvette that was placed internal to the Nd YAG laser cavity. 

Translucent bulk samples are not suitable for study, but polymer films are quite acceptable (16). With films care must be taken to properly define the true scattering angle. The use of index-matching fluids is not recommended because they are likely to alter the polymer sample. 

Readily Carbonizable Substances Determine as directed under Readily Carbonizable Substances, Appendix IIB, using 200 mg of sample dissolved in 5 mL of 95% sulfuric acid and kept at 48° to 50° for 10 min. The color is no darker than that of Matching Fluid A. 

Color A sample shows no more color than does Matching Fluid A under Readily Carbonizable Substances, Appendix 11 li. 

Stir the mixture with a glass rod until solution is complete, allow the solution to stand for 15 min, unless otherwise directed, and compare the color of the solution with that of the specified matching fluid in a comparison container that also is of colorless glass and has the same internal and cross-section dimensions, viewing the fluids transversely against a background of white porcelain or white glass. 

Matching Fluid Parts of Cobaltous Chloride CS Parts of Ferric Chloride CS Parts of Cupric Sulfate CS Parts of Water... 

Colorimetric solutions are used in the preparation of colorimetric standards for certain chemicals and for the carbonization tests with sulfuric acid that are specified in several monographs. Directions for the preparation of the primary colorimetric solutions and Matching Fluids are given under the test for Readily Carbonizable Substances, Appendix IIB. Store the solutions in suitably resistant, tight containers. 

Figure 4 H NMR spectra obtained at 300 MHz. (A) Without magnetic susceptibility matching fluid, linewidths for arginine are 200 Hz for thin-walled (75-pm i.d./ 145-pm o.d.) fused silica capillary. (B) For a thicker-walled (75-pm i.d./350-pm o.d.) fused silica capillary the linewidth is reduced to 11 Hz. (C) Linewidth of HOD (10% H20/90% D20) is less than 1 Hz with magnetic susceptibility matching fluid. (D) Microcoil configure at magic angle. Linewidth of HOD (10% H20/90% D20) is 0.6 Hz. (Reprinted with permission from Ref. 14. Copyright 1999 American Chemical Society.)...

Figure 18. Spatial frequency response of a photopolymer (37). The response is measured in terms of the efficiencies of holographic gratings. For the solid curve each efficiency was measured with the sample immersed in an index-matching fluid, so as to eliminate the effects of any modulation of the sample thickness. For the dashed curve the sample was in air. The curves show that for spatial frequencies >100 lines/mm the response of the material is almost entirely a refractive index modulation, while for <100 lines/mm there is little index modulation but there is a substantial thickness modulation.

Fig. 3 Schematic illustrating methods of coupling incident light into the waveguide, (a) Simple end firing, (b) Prism coupling, typically requires the presence of index matching fluid, (c) Grating coupling...

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